Security and digital rights experts have dumped on the home secretary's proposal for new laws that would criminalise streaming extremist content, calling the move "incredibly dangerous".

Home secretary Amber Rudd used her keynote speech at the Conservative party conference in Manchester on Tuesday to announce the new laws, which would see anyone caught "repeatedly watching" extremist content on the internet face up to 15 years jail.

"We will change the law so that people who repeatedly view terrorist content online could face up to 15 years in prison," Rudd said. "This will close an important gap in legislation."

"At present, the existing offence applies only if you have downloaded or stored such material – not if you are repeatedly viewing or streaming it online."

But the Open Rights Group said the laws would be a barrier for journalists and could stop people who are "tempted to extremism" coming to police.

“This is incredibly dangerous," Open Rights Group's director Jim Killock said in a statement soon after Rudd's speech. "Journalists, anti-terror campaigns and others may need to view extremist content, regularly and frequently.

“People tempted towards extremism may fear discussing what they have read or seen with anyone in authority. Even potential informants may be dissuaded from coming forward because they are already criminalised.”

Martha Spurrier, director of Liberty, said: “This shocking proposal would make thoughtcrime a reality in the UK. Blurring the boundary between thought and action like this undermines the bedrock principles of our criminal justice system and will criminalise journalists, academics and many other innocent people.

“We have a vast number of laws to tackle terror. The Government’s own reviewer of terror legislation Max Hill QC has said repeatedly that we need fewer, not more. A responsible Home Secretary would listen to the evidence – not grandstand for cheap political points at the expense of our fundamental freedoms.”

She went on: "In terms of how people would be identified – it’s hard for us to say without seeing more detail about the proposals. It’s likely identifying people would mean intrusive surveillance measures like those in the Investigatory Powers Act. In terms of enforceability – it’s likely to be really difficult because so many people will be caught up who have a legitimate reason and will then run that defence."

Peter Fahy, the former chief constable of Greater Manchester Police, told BuzzFeed News the proposal raised a number of questions on how it could be enforced – including whether it could interfere with the Prevent programme, given that browsing habits could serve as an early sign of someone in need of intervention.

"The issue here would be what is the definition of terrorist material and the definition of repeatedly," he said. "Unless there was protection in law the prosecution would obviously have to reveal the methods by which they gathered the evidence … [and] there could be conflicts with the world of research etc.

"I think in practise there would have to be supporting evidence to show the repeated viewing had a nefarious purposes and in practise there would probably be consideration of a Prevent intervention first."

Shashank Joshi, a research fellow at the security think tank RUSI, told BuzzFeed News that Rudd's proposal lacked specific detail and ran the risk of criminalising parts of some newspapers.

"The risk is that [Rudd] runs into the same problems as her predecessor, Theresa May, did in 2015, when she sought to ban 'extremism'," Joshi said. "These are broad and nebulous terms, and they require very careful definition in order to avoid curbing legitimate free speech.

"Otherwise we would risk criminalising some of the material that appears in certain mainstream newspaper columns."

Mark Di Stefano is a media and politics reporter for BuzzFeed News and is based in London.